mx.dns-servicio.com has no CNAME records.
Question and response
Question
dig mx.dns-servicio.com. NS
Answer
The response has no answer records.
Authority
dns-servicio.com. 244 SOA ns3.acens.net. hostmaster.ns3.acens.net. 1771941575 14400 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0